Understanding your Netalyzr results

UDP datagrams on arbitrary ports. It is hard to pinpoint to say why this communication was blocked, as some security software will do so.

Incorrect fragmentation of large UDP datagrams. This may occur as a consequence of faulty networking machinery. However, such problems rarely have significant effect on users.

UDP-based DNS requests. DNS is the system that computers use to find the website attached to a certain URL, such as www.newscientist.com. Many internet service providers run their own DNS systems and block access to UDP-based DNS, which can be used to access other DNS systems. This allows your provider to profit by serving you adverts when you mistype a domain name, rather than telling you that you got the URL wrong. This is not dangerous, but it can confuse users. It can also prevent some browser search functions from working.

Network access properties

Round-trip time. This measures the time taken for a packet of information to complete the round trip between your machine and the servers run by the International Computer Science Institute, the developers of the Netalyzr. Anything up to a few hundred milliseconds is typical. Latencies larger than 0.5 seconds are a problem and will result in slow browsing. It is, however, hard for users to fix this problem. It could be that the network is overloaded, or that packets are being sent by a circuitous and inefficient route. Users whose traffic is transmitted via satellite (as is done in some developing countries, for example) suffer inherently large latency.

Packet loss. Your browsing will slow down if packets of data go missing between your computer and your internet service provider. A likely reason is weak signal strength in wireless networks. If you can exclude this possibility and you see the problem repeatedly, contact your service provider.

Browsing speed depends in part on how quickly your computer can establish a connection with other machines. TCP setup latency measures that delay. Anything more than a few tenths of a second is less than ideal. This may be due to the distance between the Netalyzr servers and your machine, but it could also be due to other factors, such as heavy traffic on your internet service provider's network, or a poor wireless connection, in which case you may find that browsing is slow.

How well is the network around your machine functioning? Netalyzr tests to see whether packets of information are going missing. If they are, and you are using a wireless network, you should probably move closer to the base station. Wireless networks can also be disrupted by electromagnetic radiation emitted by microwaves and other devices. If this test reports a problem and you are not on a wireless network then you should contact your ISP.

More bandwidth often means faster surfing. This test measures the weakest link, or lowest bandwidth, in the chain of connections between your machine and the Netalyzr servers. Download bandwidth of less than 1 megabit per second will result in slow browsing. Upload speeds are typically less. The most basic option for users who find these reported values too low is to upgrade to a higher-bandwidth service.

Buffers are small memory stores that internet devices use when shuffling data around. If the buffering on your network is too high, then applications such as online gaming, Skype and streaming video will not work well as soon as additional traffic is present (for example, long file downloads). Buffering times of more than 0.5 seconds are less than ideal. Unfortunately, this is a difficult problem to solve. A more expensive modem or faster internet connection can help, but neither is a guaranteed solution.

HTTP tests

Some internet service providers block certain types of content, but do not always tell their customers about this. This test will reveal whether your provider is blocking music stored in the mp3 format, executable files (which when downloaded directly and not as part of a software upgrade are frequently infected with viruses) or BitTorrent files, a popular method for sharing music and video. The test also checks to see if your provider can spot a harmless virus file. If you are using anti-virus software and this file is not blocked, double-check that the software is indeed running.

Internet service providers and media outlets use stores of web pages, known as caches, to speed up browsing. If this tests reports a problem then your provider's cache may not be working properly. This could mean that you will receive outdated versions of web pages.

Some internet service providers insert adverts around the web pages that users view. If this is happening to you Netalyzr will report the presence of a "frame". This usually occurs in places that provide free wireless connections, like airports. It would be controversial for a regular provider to insert adverts in this way. If you see this warning and you are not on a free public wi-fi system, then please let us know more. There is a feedback box at the bottom of the Netalyzr results.

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